1. Field of the Invention
The present invention relates to a keyboard apparatus for enabling a user to input information to an information processing apparatus such as a computer, and more particularly to a keyboard apparatus which is a large keyboard apparatus to be used together with a desktop personal computer or the like, and in which foreign matters such as dust or liquid droplets hardly enter a gap between keys, the reliability is high, and the appearance is excellent.
The present invention also relates to an electronic apparatus having a key input apparatus to which the keyboard apparatus is applied, and a method of producing the keyboard apparatus.
2. Related Art
FIG. 11 shows an appearance of a typical example of a conventional keyboard apparatus 10, and FIG. 12 is an exploded perspective view showing the structure of the keyboard apparatus 10. As shown in FIG. 11, a top cover 160 has a structure in which a portion where keys are arranged is largely cut away, and key caps (key tops) 201 of keys (not shown) attached to a frame member which will be described later are exposed to the outside through the portion, thereby enabling a user to operate the keys. It is often that nothing is disposed in a portion 151 between adjacent keys. In order to prevent foreign matters such as dust or liquid droplets from entering the portion 151, however, it is contemplated that a member 151a which closes the portion is inserted into the portion.
Hereinafter, the structure of the conventional keyboard apparatus 10 will be described with reference to FIG. 12 which is an exploded perspective view. FIG. 12 is drawn upside down with respect to the use state of the keyboard apparatus 10, and the top cover 160 is positioned in the lower side. In a frame member 700, key receiving portions to which the keys are to be attached are formed at positions corresponding to the key layout. In FIG. 12, a part of the key receiving portions is shown in a simplified manner as a lattice-like pattern. Key movable mechanism portions 250 of the keys which will be described later are attached to the key receiving portions. A sheet switch 300 having electrical contacts serving as membrane switches which perform on/off operations in accordance with the existence/nonexistence of depression is placed on the frame member 700. A back plate 400 such as a metal-made plate serving as a reinforcing member is placed on the sheet switch 300.
In the frame member 700, a plurality of pins (in FIG. 12, reference numerals 701 to 704) are formed in the vicinities of the four corners so as to project to the lower side (in the figure, the upper side) of the keyboard apparatus, respectively. In the sheet switch 300, holes 301 to 304 which are slightly larger than each pin so as to allow the pins to pass therethrough are formed, and, in the back plate 400, holes 401 to 404 are similarly formed correspondingly with the positions of the pins. In an assembling process, the pins are passed through the holes, tip end portions of the pins made of a resin are heated so as to be melted, and then collapsed to be welded to the back plate 400, whereby the frame member 700 and the back plate 400 are coupled together in a form that the sheet switch 300 is interposed therebetween. Then, the top cover 160 is coupled with the coupled member in which the frame member 700, the sheet switch 300, and the back plate 400 are coupled together. Finally, a bottom cover 500 is coupled to complete the assembly of the keyboard apparatus 10. In addition to the vicinities of the four corners of the frame member 700, the pins may be further disposed in a plurality of other places.
Hereinafter, an example of the key movable mechanism portions 250 will be described. As a typical structure of a movable mechanism for enabling a vertical movement of a key, there is a so-called pantograph structure. FIG. 13 schematically shows the pantograph structure. Although not illustrated in the figure, a holder is attached to the upper side of the pantograph structure, and the top cover 160 is attached to the upper side of the holder. Specifically, the structure is configured in a finer manner. However, the description of the structure is omitted. Recently, the holder is not sometimes attached. When a user depresses the key cap 201 of the key as an operation for a key input, the pantograph structure of the key movable mechanism portion 250 is deformed to press a rubber spring which is not shown. Then, a switch which is in the sheet switch 300 and at the position corresponding to the key receives a pressure from the rubber spring, to enter a contact state, whereby a key input is performed. A key structure using such a pantograph structure is disclosed in many publications. An example of such publications is JP-A-11-224559 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”).
JP-A-8-212868 discloses an example in which a frame member is molded integrally with a top cover. JP-UM-A-2-5831 discloses a configuration in which the frame member is split into a plurality of pieces, as a countermeasure against curvature of a keyboard apparatus due to shrinkage of a frame member after resin molding. (the term “JP-UM-A” as used herein means an “unexamined published Japanese utility model application”).
In a conventional keyboard apparatus in which a partitioning portion is not disposed between keys, dust or liquid droplets such as spilled coffee easily enter a gap between keys. The dust entering the inside causes the sensation of depressing a key to be dispersed, and conducting the operation can be difficult. When the liquid droplets enter a switch portion, there is a possibility that the switch portion does not normally operate.
In the case where a keyboard apparatus is produced by a conventional configuration and assembling method, particularly, in the case where a frame member of a large keyboard apparatus is configured by plastic molding, shrinkage after resin molding causes a positioning error in the longitudinal direction of the frame member. When a partitioning portion is to be disposed between keys, the gap between the partitioning portion and a key cap must be set with an extra margin because of the positioning error. Although the partitioning portion is disposed, therefore, a small gap is formed between the key cap and the partitioning portion, thereby causing a problem in that the effect of preventing foreign matters such as dust or liquid droplets from entering is incompletely achieved.
After the shrinkage of a molded product settles, moreover, a situation may possibly occur where the size of the gap between the key cap and the partitioning portion is varied depending on the position in the keyboard apparatus. From the viewpoint of appearance, the situation is not preferable.
In the case where the partitioning portion is disposed as a member separate from the top cover, a gap may be formed also between the top cover and the partitioning portion. From the viewpoint of product design, a clear impression cannot be made when the keyboard apparatus is seen from the upper side. Consequently, there is a problem in that the design does not sometimes suite the taste of the user.
In a keyboard apparatus of JP-A-8-212868, a top cover and a frame member are molded integrally with each other, and hence the relative positional misfit between the top cover and the frame member does not occur. Because of the structure in which a partitioning portion is not formed between keys, however, the structure cannot prevent foreign matters such as dust or liquid droplets from entering.
In a keyboard apparatus of JP-UM-A-2-5831, a configuration is disclosed where, as a countermeasure against deformation due to shrinkage of a frame member after resin molding, the frame member is split into a plurality of pieces. However, the countermeasure is conducted in order to prevent curvature of the keyboard apparatus from occurring. A top cover structure in which a partitioning portion is disposed between keys is not disclosed. The countermeasure is not conducted for accurate alignment of key attachment positions with respect to key arrangement spaces surrounded by a partitioning portion.